JP2016180691A - Ultrasonic flowmeter with silencer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter with silencer that can reduce a change in measurement value arising from piping to be connected to an upstream side.SOLUTION: A flowmeter 10 according to the present invention includes a silencer 30 on an upstream side of a flow measurement unit 11 that transmits/receives an ultrasonic wave between paired transducers 21 and 21 opposing each other in an axial direction of a measurement flow channel 20 of a rectangular cross section. The silencer 30 is provided with: a cylindrical body 31 coaxial with the measurement flow channel 20; an annular obstacle plate 33 to be engaged with an inner peripheral surface 31M of the cylindrical body 31; a center obstacle plate 34 forming an annular clearance 34A between the inner peripheral surface 31M of the cylindrical body 31 and the center obstacle plate; and a plurality of support pillars 47 coupling the annular obstacle plate 33 to the center obstacle plate 34. When viewing from the axial direction of the cylindrical body 31, each support pillar 47 is arranged in a range where an angle formed with a straight line connecting the support pillar 47 to a center axis of the cylindrical body 31 and a long-side direction of the flow channel cross section of the measurement flow channel 20 is equal to or less than 45 degrees.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic wave with a silencer provided with a silencer on the upstream side of a flow rate measurement unit that measures the flow rate of a fluid flowing through a measurement channel by transmitting and receiving ultrasonic waves between a pair of transducers. It relates to a flow meter.

  Conventionally, as this type of ultrasonic flowmeter with a silencer, the silencer is placed in the cylindrical body coaxially with the measurement flow path, the annular obstacle wall fitted to the inner peripheral surface of the cylindrical body, The central obstacle wall that covers the central hole of the annular obstacle wall and forms an annular gap between the inner peripheral surface of the cylindrical body is arranged alternately, and the annular obstacle wall and the central obstacle wall are connected by a plurality of columns. Is known (for example, see Patent Document 1).

JP 2012-220428 A (paragraphs [0023] to [0026], FIG. 2)

  However, the above-described conventional ultrasonic flowmeter with a silencer has a problem that a change in measurement value due to a difference in the shape or the like of the pipe connected to the upstream side is large.

  This invention is made | formed in view of the said situation, and aims at provision of the ultrasonic flowmeter with a silencer which can reduce the change of the measured value resulting from the piping connected upstream.

  The inventor of the present application has made extensive studies to solve the above problems, and as a result, has obtained the knowledge that the change in the measured value depends on the arrangement of a plurality of support columns connecting the annular obstacle wall and the central obstacle wall. Specifically, the inventor of the present application, when a pair of transducers are arranged opposite to each other on the central axis of the measurement channel having a rectangular cross-section, each column and the measurement are viewed from the axial direction of the measurement channel. The angle between the straight line connecting the central axes of the flow paths and the longitudinal direction of the cross section of the measurement flow path is greater than 45 degrees and less than 90 degrees. The knowledge that change becomes small was acquired. In addition, in the case where the pair of transducers are arranged opposite to each other in a direction obliquely intersecting the central axis of the measurement flow path, the inventor of the present application has a deviation from the transducer of the support column in the circumferential direction of the measurement flow path. It was also found that the change in the measured value is smaller when the deviation is 45 degrees or more and 90 degrees or less than when it is less than 45 degrees. Based on these findings, the inventors of the present application have arrived at the inventions of claims 1 to 5 below.

  That is, in order to achieve the above object, the invention of claim 1 is directed to a flow rate measurement unit that measures the flow rate of a fluid flowing through a measurement channel by transmitting and receiving ultrasonic waves between a pair of transducers. An ultrasonic flowmeter with a silencer provided with a silencer on the upstream side, wherein the measurement flow path has a rectangular cross section, and the pair of transducers are on a central axis of the measurement flow path The silencer is disposed opposite to the cylindrical body, the cylindrical body disposed coaxially with the measurement channel, the annular obstacle plate fitted to the inner peripheral surface of the cylindrical body, and the inner side of the annular obstacle plate A central obstruction plate that covers the central hole formed in the cylindrical body and forms an annular gap between the inner peripheral surface of the cylindrical body, and the annular obstruction plate and the central obstruction plate are in the axial direction of the cylindrical body A plurality of struts connecting the annular obstruction plate and the central obstruction plate, so as to be alternately arranged, In the ultrasonic flowmeter with a silencer provided, each of the columns has a straight line connecting the column and the central axis of the cylindrical body and the measurement flow when viewed from the central axis direction of the cylindrical body. It is an ultrasonic flowmeter with a muffler arranged in a range where the angle formed with the longitudinal direction of the flow path section of the path is 45 degrees or less.

  The invention according to claim 2 is the ultrasonic flow rate with a silencer according to claim 1, wherein the plurality of struts are composed only of a pair of opposed struts arranged at positions 180 degrees apart in the circumferential direction of the cylindrical body. It is a total.

  A third aspect of the present invention is the ultrasonic flowmeter with a silencer according to the second aspect, wherein the pair of opposed struts coincide with a longitudinal direction of a cross section of the measurement flow path.

  According to a fourth aspect of the present invention, a silencer is provided with a silencer on the upstream side of a flow rate measurement unit that measures the flow rate of fluid flowing through the measurement flow path by transmitting and receiving ultrasonic waves between a pair of transducers. An ultrasonic flowmeter with a pair, wherein the pair of transducers are arranged opposite to each other in a direction obliquely intersecting a central axis of the measurement flow path, and the silencer is arranged coaxially with the measurement flow path A cylindrical body, an annular obstacle plate fitted to the inner peripheral surface of the cylindrical body, a central hole formed inside the annular obstacle wall, and an inner peripheral surface of the cylindrical body A central obstacle wall forming an annular gap therebetween, and the annular obstacle wall and the central obstacle wall so that the annular obstacle wall and the central obstacle wall are alternately arranged in the axial direction of the cylindrical body. In the ultrasonic flowmeter with a silencer, comprising a plurality of struts for connecting the plurality of struts, Is an ultrasonic flowmeter with a silencer arranged in a range in which the circumferential displacement with respect to the pair of transducers is 45 degrees or more and 90 degrees or less when viewed from the axial direction of the cylindrical body It is.

  The invention according to claim 5 is the ultrasonic flow rate with silencer according to claim 4, wherein the plurality of struts are composed only of a pair of opposed struts arranged at positions 180 degrees apart in the circumferential direction of the cylindrical body. It is a total.

  The invention according to claim 6 is the ultrasonic flowmeter with a silencer according to claim 5, wherein the facing direction of the pair of opposed struts is orthogonal to the facing direction of the pair of transducers.

[Invention of claims 1 to 3]
According to the first aspect of the present invention, the measurement channel has a rectangular cross section, and a pair of transducers are arranged opposite to each other on the central axis of the measurement channel. According to the present invention, each column that connects the annular obstacle wall and the central obstacle wall is measured with a straight line connecting the column and the central axis of the cylindrical body when viewed from the central axis direction of the cylindrical body. Since the angle formed by the longitudinal direction of the flow path section of the flow path is 45 degrees or less, it is possible to reduce the change in the measurement value due to the pipe connected to the upstream side. In addition, as in the invention of claim 2, if the plurality of struts are composed of only a pair of opposed struts arranged at positions 180 degrees apart in the circumferential direction of the cylindrical body, pressure loss due to the struts can be reduced. However, it is possible to efficiently reduce changes in measurement values. In addition, it is preferable that the opposing direction of a pair of opposing support | pillar corresponds with the longitudinal direction of the flow-path cross section of a measurement flow path (invention of Claim 3).

[Invention of Claims 4-6]
In the invention of claim 4, the pair of transducers are arranged opposite to each other in a direction that obliquely intersects the central axis of the measurement flow path. And according to this invention, when it sees from the axial direction of a cylindrical body, several support | pillars are arrange | positioned in the range from which the shift | offset | difference of the circumferential direction with respect to a pair of transmitter / receiver becomes 45 to 90 degree | times. Therefore, it becomes possible to reduce the change of the measured value resulting from the piping connected to the upstream side. In addition, as in the fifth aspect of the present invention, if the plurality of struts are composed of only a pair of opposed struts arranged at positions 180 degrees apart in the circumferential direction of the cylindrical body, pressure loss due to the struts can be reduced. However, it is possible to efficiently reduce changes in measurement values. The facing direction of the pair of facing struts is preferably orthogonal to the facing direction of the pair of transducers (invention of claim 6).

The side view of the ultrasonic flowmeter with a silencer concerning a 1st embodiment of the present invention. Cross section of ultrasonic flowmeter with silencer Perspective view of inner unit (A) Front sectional view of ultrasonic flowmeter with silencer, (B) Front sectional view of ultrasonic flowmeter with silencer as another example, (C) Ultrasonic flowmeter with silencer as reference example Front sectional view Diagram showing the outline of the confirmation experiment The graph which shows the experimental result of Experimental example 1 The graph which shows the experimental result of Experimental example 2 The graph which shows the experimental result of Experimental example 3 The figure which piled up and showed the experimental result of Experimental Examples 1-3 when an elbow pipe was done on the same graph (A) The figure which shows the flow rate distribution in the case where there is a flow velocity distribution in the longitudinal direction of the measurement flow path and the arrangement relationship between the pair of transducers, (B) The flow velocity in the case where there is a flow velocity distribution in the short direction of the measurement flow path The figure which shows distribution and arrangement relation of one pair of transducers (A) Conceptual diagram of smoothing of flow velocity distribution in turbulent flow, (B) Conceptual diagram of smoothing of flow velocity distribution in laminar flow (A) Front sectional view and (B) AA sectional view of an ultrasonic flowmeter with a silencer when the opposing direction of a pair of opposing struts and the longitudinal direction of the measurement channel are orthogonal to each other (A) Front sectional view, (B) BB sectional view of an ultrasonic flowmeter with a silencer when the opposing direction of a pair of opposing struts coincides with the longitudinal direction of the measurement flow path In the ultrasonic flowmeter with a silencer according to the second embodiment, (A) a sectional view cut in the facing direction of a pair of transducers, (B) cut in a direction orthogonal to the facing direction of the pair of transducers Cross section (A) Front sectional view of ultrasonic flowmeter with silencer, (B) Front sectional view of ultrasonic flowmeter with silencer as another example, (C) Ultrasonic flowmeter with silencer as reference example Front sectional view (A) The figure which shows the flow rate distribution in the case where there is a flow velocity distribution in the facing direction of a pair of transducers and the arrangement relationship between the pair of transducers, (B) orthogonal to the facing direction of the pair of transducers. The figure which shows the arrangement relation of the flow velocity distribution when there is a flow velocity distribution in the direction and a pair of transducers (A) Front sectional view, (B) CC sectional view when the facing direction of a pair of opposed struts coincides with the facing direction of a pair of transducers (A) Front sectional view, (B) DD sectional view in the case where the facing direction of a pair of opposed struts and the facing direction of a pair of transducers are orthogonal to each other (A) Front sectional view of ultrasonic diverter with silencer according to modification, (B) Front sectional view of ultrasonic diversion meter with silencer according to modification (A) Front sectional view of ultrasonic diverter with silencer according to modification, (B) Front sectional view of ultrasonic diversion meter with silencer according to modification

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the ultrasonic flowmeter 10 with a silencer of the present embodiment (hereinafter simply referred to as “flowmeter 10”) is attached in the middle of a pipe 70 (for example, a gas pipe) through which a fluid flows. The silencer 30 is provided on the upstream side of the flow rate measuring unit 11. In the following description, the upstream portion of the pipe 70 from the flow meter 10 is appropriately distinguished from the upstream pipe 71, and the downstream portion from the flow meter 10 is appropriately distinguished from the downstream pipe 72.

  As shown in FIG. 2, the flow rate measurement unit 11 includes a measurement tube 12 in which the measurement channel 20 is formed inside, and a pair of transducers 21 for measuring the flow rate of the fluid flowing through the measurement channel 20, 21. Specifically, the measuring tube 12 has an inner cross-sectional area that is stepwise reduced at an intermediate portion in the axial direction. The structure is sandwiched between directions. The pair of large-diameter portions 13 and 13 are provided with a pair of transducers 21 and 21 that can transmit and receive ultrasonic waves, so that they extend linearly to the inner portion of the small-diameter portion 14. The measurement flow path 20 is formed. Here, the pair of transducers 21 and 21 is disposed on the central axis of the measurement flow path 20. In FIG. 2, a mechanism for fixing the pair of transducers 21 and 21 to the measuring tube 12 is omitted.

  As shown in FIG. 4A, in this embodiment, the cross-sectional shape of the measurement channel 20 is rectangular. Specifically, the length of the measurement channel 20 is approximately the same as the length of the transducer 21 in the short direction in the cross section of the measurement channel 20, and the measurement channel 20 in the longitudinal direction. Is about 2 to 20 times the length of the transducer.

  As shown in FIG. 2, the silencer 30 has a cylindrical body 31 connected to the measurement tube 12. The cylindrical body 31 has a cylindrical shape and is arranged coaxially with the measurement pipe 12 (measurement flow path 20). The inner diameter of the cylindrical body 31 is larger than the inner diameter of the upstream pipe 71. Specifically, the inner diameter of the cylindrical body 31 is the same as the inner diameter of the large diameter portion 13 of the measuring tube 12. Further, flanges 31F and 31F are provided at both ends of the cylindrical body 31, and the flanges 31F and 31F are overlapped and connected to the flange 71F of the upstream pipe 71 and the flange 12F of the measurement pipe 12.

  Inside the cylindrical body 31, annular obstacle walls 43 and central obstacle walls 44 are alternately arranged with a certain interval, and the inside of the cylindrical body 31 is formed by the annular obstacle walls 43 and the central obstacle wall 44. It is partitioned into a plurality of rooms 36, 36,.

  The annular obstacle wall 43 has an annular shape, has a central hole 43A at the center in the radial direction, and is fitted to the inner peripheral surface 31M of the cylindrical body 31. The central obstacle wall 44 has a circular shape and forms an annular gap 44 </ b> A with the inner peripheral surface 31 </ b> M of the cylindrical body 31. Here, the size of the central obstacle wall 44 is larger than that of the central hole 43A of the annular obstacle wall 43, and the central obstacle wall 44 and the central hole 43A are arranged to face each other in the axial direction of the cylindrical body 31. Yes. Further, the annular obstacle wall 43 and the annular gap 44 </ b> A are also opposed to each other in the axial direction of the cylindrical body 31. Thus, in the present embodiment, the central obstacle wall 44 is disposed so as to cover the central hole 43A of the annular obstacle wall 43, and the central hole 43A and the annular gap 44A do not overlap in the axial direction of the cylindrical body 31. It is like that.

  As shown in FIG. 3, the annular obstacle wall 43 and the central obstacle wall 44 are connected by a plurality of support columns 47 to form an inner unit 40. The column 47 rises from the flange wall 41 having a diameter larger than that of the annular obstacle wall 43 and extends in the axial direction of the cylindrical body 31, penetrates the annular obstacle wall 43 and the central obstacle wall 44, and The distance between the central obstacle wall 44 and the central obstacle wall 44 is fixed. As shown in FIG. 2, the inner unit 40 is inserted from the opening 32 on the upstream side of the cylindrical body 31, and the flange wall 41 is interposed between the flange 31 </ b> F of the cylindrical body 31 and the flange 71 </ b> F of the upstream pipe 71. It is positioned in the cylindrical body 31 by being sandwiched between the two. Note that the circular hole 41A formed through the central portion of the flange wall 41 has the same diameter as the central hole 43A, for example (see FIG. 2).

  In the present embodiment, the plurality of support columns 47 are configured by only a pair of opposed support columns 47T and 47T disposed in pairs at positions 180 degrees apart in the circumferential direction of the cylindrical body 31. Thus, in this embodiment, since the number of the support | pillars 47 which connect the cyclic | annular obstacle wall 43 and the central obstacle wall 44 is only two, it becomes possible to reduce the pressure loss of the fluid by the support | pillar 47. Yes.

  As shown in FIGS. 4A and 4B, each counter column 47 </ b> T is a straight line L <b> 1 connecting the counter column 47 </ b> T and the central axis of the cylindrical body 31 when viewed from the axial direction of the cylindrical body 31. And the angle formed by the longitudinal direction of the channel cross section of the measurement channel 20 is arranged in a range of 45 degrees or less. In other words, the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20 is 45 degrees or less. 4A and 4B, the angle formed between the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20 is 0 degrees (ie, Those in which both directions coincide with each other) and 45 degrees are shown. 4C, as a reference example not belonging to the technical scope of the present invention, an angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20 is shown. Is shown at 90 degrees.

  This completes the description of the configuration of the flow meter 10 according to the present embodiment. Next, the effect of the flow meter 10 will be described.

  In the flow meter 10 of the present embodiment, the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20 is 45 degrees or less (FIG. 4A and FIG. Therefore, as described in the following [Confirmation Experiment], it is possible to reduce the change in the measurement value caused by the pipe connected to the upstream side. In addition, in the present embodiment, since the plurality of support columns 47 include only a pair of opposed support columns 47T and 47T, it is possible to efficiently reduce the change in the measurement value while reducing the pressure loss due to the support columns 47. The angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel is preferably 0 degrees (see FIG. 4A).

[Confirmation experiment]
The effect of the flow meter 10 according to the present invention was confirmed by experiments. Specifically, as shown in FIG. 5, a test pipe 81 is connected to the upstream side of the flow meter 10, a straight pipe 82 is connected to the downstream side, and a standard device 85 is attached to the downstream side of the straight pipe 82. . Then, the room air was sucked by the blower 83 connected to the downstream side of the straight pipe 82, and the difference between the measured values of the flow meter 10 and the standard device 85 was measured. Experimental conditions and experimental results are as follows.

[Experimental conditions]
The arrangement of the pair of opposing struts 47T and 47T in the flow meter 10 is the arrangement shown in FIGS. 4A and 4B, and experimental examples 1 and 2 were used. In addition, in the flow meter 10, the arrangement of the pair of opposed struts 47T and 47T having the arrangement shown in FIG. Regarding the flow rate, when the maximum suction amount of the blower 83 is 100%, the suction amount is changed in the range of 0 to 100%, and the air flow rate is changed. And about the experimental examples 1-3, the gap | deviation of the measured value in each flow volume was measured. As the test pipe 81, two types of a straight pipe and an elbow pipe were used (an example of an elbow pipe is shown in FIG. 5). As the standard device 85, a critical nozzle was used. The room temperature during the test is 23 ° C., the room pressure is atmospheric pressure, and the room humidity is 50% RH.

[Experimental result]
Experimental results of Experimental Examples 1 to 3 are shown in FIGS. 6 to 8, the deviation (%) in the measurement value on the vertical axis is the difference between the measurement value of the flow meter and the measurement value of the standard device 85 in each of Experimental Examples 1 to 3, and the measurement value of the standard device 85. It was calculated by dividing. As shown in FIGS. 6 to 8, in any of Experimental Examples 1 to 3, the deviation (%) in the measured value is large when the flow rate is in the range of 0 to 30%. In addition, in the range of 0 to 30% of the flow rate, in each of the experimental examples 1 to 3, the measured value deviation (when the elbow pipe is used as the test pipe 81 is smaller than when the straight pipe is used) %) Is larger.

  In FIG. 9, the range of the flow rate of 0 to 40% as a result of Experimental Examples 1 to 3 in the case where an elbow pipe is used as the test pipe 81 is shown in an enlarged manner. As shown in the figure, the deviation (%) in the measured value is when the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20 is 90 degrees (FIG. 4 (C)), −0.69% to 0.88%, 45 degrees (see FIG. 4B), −0.41% to 0.56%, 0 degrees (see FIG. 4B). 4 (A)), it is -0.46% to 0.31%, and it can be seen that the deviation (%) in the measured value decreases as the angle formed by both directions decreases. From this, when the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20 is 45 degrees or less, the angle is larger than 45 degrees. It was confirmed that the change in measured value due to the upstream pipe (test pipe 81) was reduced.

  In addition, about the cause of the effect of the flowmeter 10, the following is estimated. Before explaining this guess, first consider the case where there is no silencer 30. In this case, as shown in FIG. 10A, if there is a fluid flow velocity distribution in the longitudinal direction of the cross section of the measurement flow path 20, the ultrasonic waves transmitted and received by the pair of transducers 21 and 21 are Only the part of the fluid flowing at a certain flow velocity passes, and the flow velocity distribution is not reflected in the ultrasonic wave passage region. For this reason, it becomes difficult to measure the average value of the flow velocity of the fluid, and the flow rate measurement value becomes difficult to stabilize. As shown in FIG. 10B, when there is a fluid flow velocity distribution in the short direction of the cross section of the measurement flow channel 20, the ultrasonic waves transmitted and received by the pair of transducers 21 and 21 are transmitted. Since the flow velocity distribution is reflected in the passage region, it is possible to measure the average value of the flow velocity, and the flow rate measurement value is easily stabilized. As described above, the flow velocity distribution of the fluid can be considered as a cause of the change in the flow rate measurement value.

  Next, consider the case where the silencer 30 is present. When the silencer 30 is present on the upstream side of the flow rate measuring unit 11, the fluid moves between the radially central side and the radially outer side of the cylindrical body 31 by the annular obstacle wall 43 and the central obstacle wall 44. It flows like a meander. As described above, in the silencer 30, compared to the case where the fluid flows linearly in the axial direction of the cylindrical body 31, the distance through which the fluid flows becomes longer, and thus the flow velocity distribution of the fluid is easily smoothed. 11A and 11B conceptually show smoothing of the flow velocity distribution when the fluid flow is a turbulent flow and when it is a laminar flow (FIG. 11A). In FIG. 11B, the size of the arrow represents the size of the flow velocity.

  Incidentally, it is generally known that laminar flow is likely to occur when the flow velocity is relatively low, and turbulent flow is likely to occur when the flow velocity is relatively high. Therefore, in the transition region where the laminar flow and the turbulent flow are switched, any smoothing shown in FIGS. 11 (A) and 11 (B) hardly occurs, and the smoothing effect by the silencer 30 may be reduced. . In the experimental results shown in FIG. 6 to FIG. 8, the cause of the large deviation (%) in the measured value in the flow rate range of 0 to 30% is that the fluid flow is in the transition region. Presumed to be the cause.

  Here, in the case where there is a fluid flow velocity distribution in the longitudinal direction of the cross section of the measurement flow path 20, the opposing direction of the pair of opposed struts 47T and 47T and the longitudinal direction of the cross section of the measurement flow path 20 are formed. When the angle is 90 degrees, as shown in FIG. 12, the flow of the fluid is divided into a portion having a high flow velocity and a portion having a low flow velocity by the opposing struts 47T and 47T (in FIG. 12, the size of the arrow indicates the magnitude of the flow velocity. Represents.) Accordingly, the fluid flowing in the silencer 30 moves from the radial center side of the cylindrical body 31 to the radially outer side and returns to the radial center side again. It is difficult to mix, and it is expected that the time required for smoothing the flow velocity distribution will increase.

  On the other hand, if the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement flow path 20 is 0 degrees, as shown in FIG. The fluid divided by the above has a flow velocity distribution similar to the flow velocity distribution before being divided by the opposing struts 47T and 47T (in FIG. 13, the size of the arrow represents the size of the flow velocity). Accordingly, the portion where the flow velocity distribution is fast and the portion where the flow velocity distribution is slow are easily mixed until the cylindrical body 31 moves from the radially central side to the radially outer side and returns to the radial central side again, and the flow velocity distribution is smoothed. It is expected that the time required for the process will be shortened.

  In summary, the time required for smoothing the flow velocity distribution by the silencer 30 depends on the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the cross section of the measurement channel 20. It will change. This change is considered to be particularly remarkable in the transition region between laminar flow and turbulent flow. And when the angle which the opposing direction of a pair of opposing support | pillar 47T and 47T and the longitudinal direction of the flow-path cross section of the measurement flow path 20 becomes in the range of 0 degree-45 degree | times, the angle is 45 degree-90 degree | times. It is considered that the time required for smoothing is shorter than when it is within the range. And it is estimated that this difference in time required for smoothing appears as a difference (%) in the measured values in Experimental Examples 1 to 3.

[Second Embodiment]
Hereinafter, a second embodiment of the present embodiment will be described with reference to FIGS. As shown in FIGS. 14 (A) and 14 (B), the ultrasonic flow meter with silencer 10V of the present embodiment (hereinafter simply referred to as flow meter 10V) mainly has a configuration of the flow measurement unit 11V. It differs from the structure of the flow volume measurement part 11 of the said 1st Embodiment. Specifically, the measurement flow path 20V has a circular cross section, and the pair of transducers 21 and 21 are arranged to face each other in a direction obliquely intersecting the central axis of the measurement flow path 20. The measuring tube 12 is fixedly provided.

  In the present embodiment, when the plurality of support columns 47 are viewed from the axial direction of the cylindrical body 31, the circumferential displacement with respect to the pair of transducers 21 and 21 is in a range of 45 degrees or more and 90 degrees or less. (See FIGS. 15A and 15B). Specifically, in the present embodiment, as in the first embodiment, the plurality of support columns 47 are configured by only a pair of opposed support columns 47T and 47T, and when viewed from the axial direction of the cylindrical body 31, The angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the opposing direction of the pair of transducers 21 and 21 is 45 degrees or more and 90 degrees or less. 15A and 15B, the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the longitudinal direction of the channel cross section of the pair of transducers 21 and 21 is shown. 90 degrees (ie, both directions are orthogonal) and 45 degrees are shown. In FIG. 15C, as a reference example not belonging to the technical scope of the present invention, the angle formed by the opposing direction of the pair of opposing struts 47T and 47T and the opposing direction of the transducers 21 and 21 is 0. Degrees are shown.

  Since the other configuration of the flow meter 10V is the same as that of the first embodiment, description thereof is omitted by attaching the same reference numerals. According to the present embodiment, it is possible to achieve the same effect as the above-described embodiment.

  In addition, the following is estimated about the cause of the effect of the flowmeter 10V. Also in the description of this guess, as in the case of the first embodiment, first consider the case where the silencer 30 is not provided. In this case, as shown in FIG. 16A, if there is a flow velocity distribution of the fluid in the opposing direction of the pair of transducers 21 and 21, the ultrasonic waves that are transmitted and received by the pair of transducers 21 and 21. Since the flow velocity distribution is reflected in the passage area of the, the average value of the flow velocity can be measured, and the flow rate measurement value can be easily stabilized. On the other hand, as shown in FIG. If there is a flow velocity distribution of the fluid in a direction orthogonal to the opposing direction of 21 and 21, the flow velocity distribution is not reflected in the ultrasonic wave passing region. For this reason, it becomes difficult to measure the average value of the flow velocity of the fluid, and it becomes difficult to stabilize the flow rate measurement value.In this embodiment as well, the flow velocity distribution of the fluid is one factor that causes the flow rate measurement value to change. Conceivable. In FIGS. 16A and 16B, the size of the arrow indicates the size of the flow velocity.

  Next, consider the case where the silencer 30 is present. As in the first embodiment, in the silencer 30, the fluid flows through the cylindrical body 31 while meandering, so that the fluid flows compared to the case where the fluid flows linearly in the axial direction of the cylindrical body 31. The flowing distance becomes long, and the flow velocity distribution of the fluid is easily smoothed.

  Here, when there is a fluid flow velocity distribution in a direction orthogonal to the facing direction of the pair of transducers 21 and 21 when viewed from the axial direction of the cylindrical body 31, the facing of the pair of facing struts 47T and 47T. When the angle formed by the direction and the opposing direction of the pair of transducers 21 and 21 is 0 degree, as shown in FIG. (In FIG. 17, the size of the arrow represents the size of the flow velocity). Therefore, it is difficult for the fluid flowing in the silencer 30 to mix the fast flow rate distribution portion and the slow flow velocity distribution portion, and the time required for smoothing the flow velocity distribution is expected to increase.

  On the other hand, when viewed from the axial direction of the cylindrical body 31, the facing direction of the pair of opposing struts 47T, 47T and the facing direction of the pair of transducers 21, 21 are orthogonal to each other in FIG. As shown, the fluid divided by the opposed struts 47T and 47T has a flow velocity distribution similar to the flow velocity distribution before being divided by the opposed struts 47T and 47T (in FIG. 18, the size of the arrow is the flow velocity). Represents the size.) Therefore, it is expected that the fluid flowing in the silencer 30 is likely to be mixed with a portion where the flow velocity distribution is fast and a portion where the flow velocity distribution is slow, and the time required for smoothing the flow velocity distribution is shortened.

  In summary, the time required to smooth the flow velocity distribution by the silencer 30 is equal to the opposing direction of the pair of opposing struts 47T and 47T when viewed from the axial direction of the cylindrical body 31, and the pair of transducers. It is thought that it changes depending on the angle between the opposing direction of 21 and 21. When the angle formed between the facing direction of the pair of opposing struts 47T and 47T and the facing direction of the pair of transducers 21 and 21 is in the range of 45 to 90 degrees, the angle is 0 to 45 degrees. It is considered that the time required for smoothing is shorter than that in the range.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various modifications are possible within the scope of the invention other than the following. It can be changed and implemented.

  (1) In the first embodiment, the structure includes only two support columns 47. However, when viewed from the axial direction of the cylindrical body 31, each support column 47 includes the support column 47 and the cylindrical body 31. As shown in FIGS. 19A and 19B, if the angle formed by the straight line connecting the central axis of the channel and the longitudinal direction of the cross section of the measurement channel 20 is 45 degrees or less. Moreover, the structure provided with three or more may be sufficient. In this case, the plurality of struts 47 may include a pair of opposing struts 47T and 47T or may not include a pair of opposing struts 47T and 47T.

  (2) In the second embodiment described above, only two support columns 47 are provided. However, when viewed from the axial direction of the cylindrical body 31, the circumferential direction relative to the pair of transducers 21, 21 is shown. If each support | pillar 47 is arrange | positioned in the range from which a shift | offset | difference is 45 degree | times or more and 90 degrees or less, as shown to FIG. 20 (A) and FIG. 20 (B), the structure provided with three or more may be sufficient. In this case, the plurality of struts 47 may include a pair of opposing struts 47T and 47T or may not include a pair of opposing struts 47T and 47T.

  (3) In the above embodiment, the central obstacle wall 44 is circular, but may be rectangular or elliptical. In the above embodiment, the circular obstacle wall 43 is circular, but it may be rectangular or elliptical.

  (4) In the above-described embodiment, a plurality of annular obstacle walls 43 and a plurality of central obstacle walls 44 are provided.

10,10V Ultrasonic flowmeter with silencer 11,11V Flow measurement unit 20,20V Measurement flow path 21,21V Transceiver 30 Silencer 43 Annular obstacle wall 44 Central obstacle wall 47 Post 47T Opposite post

Claims (6)

This is an ultrasonic flowmeter with a silencer equipped with a silencer on the upstream side of the flow rate measurement unit that measures the flow rate of the fluid flowing through the measurement flow path by transmitting and receiving ultrasonic waves between a pair of transducers. And
The measurement flow path has a rectangular cross section, and the pair of transducers are arranged opposite to each other on the central axis of the measurement flow path,
In the silencer,
A cylindrical body disposed coaxially with the measurement channel;
An annular obstacle plate fitted to the inner peripheral surface of the cylindrical body;
A central obstacle plate that covers a central hole formed inside the annular obstacle plate and forms an annular gap with the inner peripheral surface of the cylindrical body;
A plurality of support columns connecting the annular obstacle plate and the central obstacle plate are provided so that the annular obstacle plate and the central obstacle plate are alternately arranged in the axial direction of the cylindrical body. In ultrasonic flowmeter with silencer,
When viewed from the central axis direction of the cylindrical body, each of the columns has an angle formed by a straight line connecting the column and the central axis of the cylindrical body and the longitudinal direction of the cross section of the measurement channel. An ultrasonic flowmeter with a silencer arranged in a range of 45 degrees or less.   2. The ultrasonic flowmeter with a silencer according to claim 1, wherein each of the plurality of support columns includes only a pair of opposed support columns disposed at positions 180 degrees apart in a circumferential direction of the cylindrical body.   The ultrasonic flowmeter with a silencer according to claim 2, wherein the pair of opposed struts are aligned with a longitudinal direction of a cross section of the measurement flow path. This is an ultrasonic flowmeter with a silencer equipped with a silencer on the upstream side of the flow rate measurement unit that measures the flow rate of the fluid flowing through the measurement flow path by transmitting and receiving ultrasonic waves between a pair of transducers. And
The pair of transducers are arranged to face each other in a direction that obliquely intersects the central axis of the measurement flow path,
In the silencer,
A cylindrical body disposed coaxially with the measurement channel;
An annular obstacle plate fitted to the inner peripheral surface of the cylindrical body;
A central obstacle wall that covers a central hole formed inside the annular obstacle wall and that forms an annular gap with the inner peripheral surface of the cylindrical body;
A plurality of support pillars connecting the annular obstacle wall and the central obstacle wall are provided so that the annular obstacle wall and the central obstacle wall are alternately arranged in the axial direction of the cylindrical body. In ultrasonic flowmeter with silencer,
The plurality of struts are equipped with a silencer that is disposed in a range in which a deviation in a circumferential direction with respect to the pair of transducers is 45 degrees or more and 90 degrees or less when viewed from the axial direction of the cylindrical body. Ultrasonic flow meter.   5. The ultrasonic flowmeter with a silencer according to claim 4, wherein the plurality of struts include only a pair of opposed struts disposed at positions 180 degrees apart in a circumferential direction of the cylindrical body.   The ultrasonic flowmeter with a muffler according to claim 5, wherein an opposing direction of the pair of opposing columns is orthogonal to an opposing direction of the pair of transducers.